Object motion detection becomes more and more important nowadays. For example, for security and/or management purposes, a user may want to detect any object motion in the user's house; a manager of a supermarket may want to detect any object motion in the supermarket; and a nurse in a hospital may want to detect any motion of a patient in the hospital.
Existing systems and methods for detecting object motions cannot provide enough accuracy and often lead to false alarms. Existing approaches include those based on passive infrared (PIR), active infrared (AIR) and Ultrasonic. PIR sensors are the most widely used motion sensor in home security systems, which detect human motions by sensing the difference between background heat and the heat emitted by moving people. However, solutions based on PIR sensors are prone to false alarms due to its sensitivity to environmental changes, like hot/cold air flow and sunlight. They are easily defeated by blocking the body heat emission (wearing a heat-insulating full-body suit). Also, their range is limited and need line-of-sight (LOS), and thus multiple devices are needed. In AIR based approaches, an IR emitter sends a beam of IR which will be received by an IR receiver. When the beam is interrupted, a motion is detected. However, this kind of approaches can be easily seen using a regular camera or any IR detection mechanism and also has limited range and thus need LOS. Ultrasonic sensors detect human motion by sending out ultrasonic sound waves into a space and measuring the speed at which they return, and motion can be detected if there exist frequency changes. However, this kind of approaches can be defeated by wearing an anechoic suit. Also, ultrasound cannot penetrate solid objects such as furniture or boxes and cause gaps in detection field. Slow movements by a burglar may not trigger an alarm, too.
Thus, existing systems and methods for detecting object motions are not entirely satisfactory.